Re: 40% performance regression SPEC2006/leslie3d on gcc-4_2-branch

["Richard Guenther" <richard dot guenther at gmail dot com>]

On 2/18/07, Daniel Berlin <dberlin@dberlin.org> wrote:
> On 2/17/07, H. J. Lu <hjl@lucon.org> wrote:
> > On Sat, Feb 17, 2007 at 01:35:28PM +0300, Vladimir Sysoev wrote:
> > > Hello, Daniel
> > >
> > > It looks like your changeset listed bellow makes performance
> > > regression ~40% on SPEC2006/leslie3d. I will try to create minimal
> > > test for this issue this week and update you in any case.
> > >
> >
> > That is a known issue:
> >
> > http://gcc.gnu.org/ml/gcc/2007-01/msg00408.html
>
> Yes, it is something we sadly cannot do anything about without doing a
> very large number of backports.
>
> There were some seriously broken things in 4.2's aliasing that got
> fixed properly in 4.3.
> The price of fixing them in 4.2 was a serious performance drop.

There's the option of un-fixing them to get back to the state of 4.1 declaring
them fixed in 4.3 earliest.

Richard.